The use of intravascular catheters for treatment of the body is well known in the field of medicine. The need for a choice of catheter sizes and types has grown rapidly as the techniques for their use have been greatly improved and the types of medical uses have expanded quickly. One such catheter is a guide catheter which includes a tubular member having a lumen therethrough. Guide catheters are commonly used in diagnostic and treatment techniques related to vascular disease such as angioplasty. A guide catheter is inserted into the femoral artery and routed to a location near a treatment or diagnostic site through the aorta over the aortic arch to the ostium of a target vessel. The guide catheter provides a conduit so that fluid or another medical device can be delivered easily to the proximate location of treatment via the lumen of the guide catheter.
Prior art catheters often comprise a tubular member including a pair of congruent tubes, the inner one defining the lumen. A hub is connected at the proximal end of the tubes which in addition to providing access to the lumen for fluids and the like, is often used to provide torques and other necessary pressures to the tubes during their placement within the body. A tip of a selected design is placed at the distal end of the tubes. Flexibility is an essential part of the catheter so that it may be successfully torqued, pushed and pulled on its way through the vascular passage to the desired site in the body. For control of the catheter and to prevent its kinking from excessive flexing a certain amount of rigidity is also required. The prior art catheters often meet this need for rigidity by adding a support member between the two tubes. This support member may comprise a braid of metal wire wrapped around the inner tube, and often imbedded within the outer tube.
As specific examples of the type of prior art catheters described above, note U.S. Pat. No. 3,485,234, issued Dec. 23, 1969, to R. C. Stevens, for Tubular Products and Method of Making Same; and European Patent Application, Publication No. 0 277 366/A1, Priority Jun. 1, 1987, by Bruce H. Ward, for Guiding Catheter and Method for Making it. Each of these references teaches, in general, the prior art type of catheter discussed above.
One problem that has arisen is that as it becomes desirable to increase the diameter of the catheter lumen, it also becomes desirable to decrease the thickness of the walls of the tubes that form the catheter. However, it has been found that in thinner-walled catheters it is more difficult to prevent the kinking of the catheter. This negative effect on flexibility is overcome by the above cited co-pending Application, Ser. No. 08/108,973, filed Aug. 18, 1993, entitled "Improved Thin-Walled Catheter" which is incorporated by reference herein. The disadvantage of the prior art was overcome by providing a high tensile, stainless steel braid as the support structure. However, it has been found that the use of the high tensile metal braid may cause an additional problem for practitioners of the catheter art. It has been seen that the high tensile wire has a tendency to flare or spring out in an area proximate the ends of the braid both before and during the heating process used in joining the catheter to a tip or other apparatus. In a similar way, this flaring and springing of the support braid wire is found in prior art catheters even when using the lower tensile type of wire. This flaring will interfere in the proper joinder of the catheter to, for example, a tip and is clearly undesirable and unacceptable in an intravenous catheter.
It is recognized that guide catheters preferably have a low friction inner lumen for improved passage of other catheter devices, such as an angioplasty catheter, through such lumen. Catheters incorporating a lumen lined with polytetrafluoroethylene (PTFE) to insure low friction are generally known. The soft atraumatic tip of prior art catheters, however, does not incorporate a polytetrafluoroethylene liner. Due to the softness of the tip material and the absence of the PTFE liner, the tip area can add significant friction opposition to advancing devices through the inner lumen of the catheter. Further, it is recognized that extending the braid wire into the atraumatic tip is not desirable, as this would significantly stiffen the tip area and counter its function of providing an atraumatic positioning of the distal end of the guide catheter. Thus, it is the clinical function of the tip that requires such tip to be very soft and free of wire braid. Terminating the braid prior to the soft tip increases the prevalence of problems associated with the flaring or springing out of the wire braid proximate its free ends near the distal tip.
Accordingly, the need exists for a catheter tube construction incorporating a lubricous liner and overlying wire braid structure, wherein the free ends of the wire braid proximate the location of attachment of a soft atraumatic tip are prevented from flaring out during manufacture of the catheter tube. Further, a need exists for an atraumatic tip design which incorporates a lubricous liner to reduce the friction caused by the soft tip material when passing devices through the lumen of the tip. The present invention addresses these needs, as well as other problems associated with existing guide catheter tube and tip designs. The present invention also offers further advantages over the prior art and solves other problems associated therewith.